In, for example, clean rooms in semiconductor manufacturing factories, the quantity of particles dispersed in the air within the room is monitored using a particle detecting device. In research and development of particle detecting devices, the correspondence between the quantity of particles dispersed in the air within the test environment and the results of detection by the particle detecting device is examined. At this time, it is desirable to be able to control accurately the quantity of particles dispersed in the air in the test environment. (See, for example, Japanese Unexamined Patent Application Publication 2004-159508, Japanese Unexamined Patent Application Publication 2008-22764, and Japanese Unexamined Patent Application Publication 2008-22765.)